The invention relates to an optical medical instrument, in particular an endoscope or exoscope. In particular, the invention relates to an optical medical instrument of the type comprising an elongate tubular shaft, a heat source generating lost heat, a heat pipe extending inside the shaft in the longitudinal direction of the shaft and having a distal heat pipe end and a proximal heat pipe end, wherein the heat pipe is thermally coupled to the heat source in order to collect heat from the latter and remove the heat from the heat source.
Endoscopes are used in the context of minimally invasive surgery as viewing instruments. The elongate shaft of an endoscope is inserted partially into the body through an artificially created or natural opening.
An exoscope is a viewing instrument which is used for imaging in open surgery. An exoscope is placed completely outside the body, at a distance from the operating site, by means of a holding arm.
Nowadays, endoscopes and exoscopes are often designed as video endosopes and video exoscopes,respectively, and are accordingly equipped with electronic components such as image sensors, control electronics for the image sensors and/or light sources such as LEDs for lighting. During operation, the electronic components generate lost heat and thus constitute one or more heat sources. The lost heat has to be removed from the one or more heat sources via a heat transfer to the environment. The removal of the heat is necessary to protect the electronic components from overheating and from resulting loss of performance and even damage. Moreover, in the case of an endoscope, at least the portion of the shaft inserted into the body must not heat to such an extent that there is a risk of causing patient injuries. An endoscope used in surgery is subject to the provisions of the Medical Devices Act. According to the Medical Devices Act, the outside of the endoscope shaft must not exceed a temperature of 41° C., so as to avoid heat-induced damage to tissue in the human or animal body.
Without a dedicated heat removal management system, the heat transfer from the heat source to the environment takes place by free convection or thermal radiation. For this heat transfer, the surface of the instrument is available as an interface to the environment. However, as a result of the local position of the heat source or heat sources, the surface is not uniformly heated. Local temperature maxima and minima occur. Therefore, the surface of the instrument is not integrated uniformly in the process of heat removal to the environment. In particular, the locations of the temperature maxima furthermore exceed the permissible temperatures, while the potential of the temperature minima remains unused. In view of the increased use of high-performance electronics in optical medical instruments such as endoscopes and exoscopes, this localized heat transfer will in future be no longer sufficient to adequately cool the electronics.
A further disadvantage lies in a high temperature gradient, which results from the uneven heat transfer to the environment, i.e. a high temperature difference between heat source and environment. The high temperatures at the heat source, i.e. the electronics, have a negative effect on the performance of the electronics.
In the document DE 10 2010 024 003 A1, an endoscope is described that has a heat pipe through which the lost heat generated by a light source arranged in the distal area of the shaft is dissipated in the proximal direction, wherein the heat pipe extends as far as a headpiece at the proximal end of the shaft, wherein a heat sink body is arranged in the headpiece, which heat sink body is thermally coupled to the heat pipe, collects the lost heat from the heat pipe and releases it to the environment either directly or via the housing of the headpiece. In order to avoid a situation where the distal end of the shaft heats to a temperature above the maximum permissible temperature of 41° C., provision is further made that the shaft is thermally insulated on the inside from the heat pipe.
If the heat source is a powerful electronics unit that generates a lot of lost heat, this heat removal management system of the known endoscope is of limited use and, in particular if the heat source is located in the distal area of the shaft, does not ensure adequate removal of heat from the heat source.
Moreover, US 2008/0151046 A1 describes an endoscope in which, in order to remove lost heat from a light source arranged in the distal area of the shaft, a heat pipe is present that extends in the proximal direction from the distal light source, to which the heat pipe is thermally coupled, along a short partial length of the shaft, wherein a heat-conducting wire, for example a copper wire, is connected to the proximal end of the heat pipe, wherein the wire extends farther in the proximal direction and has its proximal end connected thermally conductively to the inner face of the shaft of the endoscope. The heat is transferred to the endoscope shaft only in punctiform fashion via the end of the wire, as a result of which the heat removal to the environment likewise only takes place in punctiform fashion, which represents an inadequate removal of heat in cases where there are considerable amounts of heat present.